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. _ 31 July 2000 <br /> AGE-NC Project No. 98-0468 <br /> Page 10 of 11 <br /> 4.5. EQUIPMENT DECONTAMINATION <br /> All sampling tools used for sample collection will be thoroughly rinsed with clean water after being <br /> washed with a solution of Alconox. All down-hole drilling and sampling equipment will be pressure <br /> washed prior to*starting the boring. <br /> 4.6. GROUND WATER MONITORING PROCEDURES <br /> Groundwater sample collection will be performed in accordance with PHS-EHD guidelines (San <br /> Joaquin County Public Health Services Environmental Health Division Well Standards) and <br /> CVRWQCB guidelines (Tri-Regional Water Quality Control Board Recommendations for <br /> Preliminary Investigations and Evaluation of Underground Storage Tanks). <br /> 4.6:1. Static Water Level Measurements <br /> -Prior to all ground water purging and sampling, static water levels in each well will'be measured <br /> using an electric water level indicator. Water level data will be recorded to the nearest 0.01 foot from . <br /> a.reference point marked on-the top of each PVC well casing. _Before and after each use, the <br /> measurement device will be rinsed with clean tap water. <br /> 4.6.2. Well Evacuation <br /> Subsequent to measurement of depth to water and prior to sampling, each well will be purged using, ' <br /> a bailer or submersible pump to ensure that the sample is representative of the surrounding aquifer <br /> ground water. The well will be purged until: 1) a minimum of three casing volumes is removed from <br /> the well; and/or 2)the field-measured ground water parameters have stabilized. However, if the well <br /> is purged dry prior to evacuating three casing volumes, a ground water sample will be collected <br /> following 80 percent recovery of ground water within the well or within 24-hours of well evacuation. <br /> 4.6.3. Sample Withdrawal <br /> Water samples will be collected from each monitoring well using a new, pre-cleaned disposable ' <br /> polyethylene bailer. These bailers are disposed of after one use and require no'decontaminating, <br /> thereby minimizing cross contamination due to sampling devices. Samples will be drawn and <br /> collected in such a manner that agitation and exposure of the groundwater to the atmosphere is <br /> minimal. Sample containers will be filled using the appropriate.disposable sampling attachment <br /> which allows controlled flow out of the bottom of the bailer by lifting the check valve. <br /> Advanced CcoEnvironmental,Inc. <br />